Correct. I don't play those systems anymore though. In the games I play, success and failure are determined simultaneously. Failures complicate the scene while success make it easier.
Sure, but that's a new and different definition of both 'success' and 'failure' that you have just introduced. When I was defining success, I defined it as 'doing what you wanted to do'. Whether or not your intended action would ultimately make things more or less easy isn't related to whether or not you succeeded in your action. I'm pretty sure I can sustain that from examples from last night's play:
1) The party was in a fairly narrow canyon. Ahead they saw a spring with a herd of herbivorous dinosaurs grazing and drinking water. The party decided it would be easier to ferry the party over the herd using their one flying mount than to back track and try to find away around. This plan was implemented successfully, but it made the situation worse because the low flying predatory mount ended up panicing the herd back toward where the party was hiding. Also the flying mount scared off two small ambush predators (wood drakes) that had been hiding on the cliff top waiting suitable prey. No disasters occurred as the party had been wary and everything worked out in the long run, but the successful plan didn't make the scene immediately easier.
2) The party found a hut suspended in midair high above the canyon floor. They found themselves in a missile duel with the huts bow wielding inhabitants as part of a long running feud. The party hunter began climbing up a stone spire from which the hut was suspended in order to gain a vantage point where the parties enemies wouldn't have partial cover, and possible to gain access to the hut itself. While he was implementing this plan successfully, two other party members decided to implement a plan where they would bring the whole hut down by turning part of the stone spire into mud. They ultimately implemented this plan successfully, but now the hunter's successful plan of being on the spire was complicating the scene, leading to some hijinks while he tried to get back down the stone spire and avoid getting buried in the literally hundreds of cubic feet of mud that was sloughing off the spire.
So by "success" I only mean that the players proposal succeeded. Players may propose plans that get themselves into trouble, and even though their intention succeeds it won't necessarily make the scene easier. Likewise, there are times when failures to implement a plan actually work out better in the long run. As a DM and not a real god, I have no way of knowing exactly how the game is going to play out in the future, and thus don't trust myself to always accurate predict what things are going to make the scene come out more or less favorably. For example, bringing the hut down was a very clever plan, but because it was destructive it made finding treasure harder, leaving the PC's with less loot than they might have otherwise obtained. The very successful plan therefore in some sense complicated the scene.
I find them silly in the same way that I find critical hits silly. They don't particularly add any drama to the scene, they just make light of the struggle.
I agree that this is sometimes true. But during a fight with a tyrannosaur last night, that same hunter got a timely critical hit that might have saved the life of the party's sorcerer who at the time was about to be swallowed. The player certainly enjoyed and was satisfied by that conclusion. And while fumbles in my game rarely add to the drama directly, they do help create a visual mental record of the drama. The same to some extent is true of criticals, because they stand out in the mind's of the participants.
Wicket's sling scene is a fumble because it only effects him. It doesn't escalate the challenge. Han Solo's stick snap escalated the scene and made it more challenge for everyone, not just him. The same is true of R2D2. Same is true of Han Solo's talking problems. The "failure of the roll" made the scenes more complicated for everyone involved, not just the character who "rolled the dice." A fumble is a personal experience that only impacts that character directly. In my mind/experience that's silly.
I'm not sure you can draw such a bright line in practice between what effects only you and what escalates the challenge. For example, if the party had tried to flee the tyrannosaurus, it's possible that an ally would have stumbled and fell. This was a personal failure, but if the rest of the party valued the ally enough to want to rescue him, the personal failure leads to a scene complication. And that sort of thing happens all the time in my game even though my game only has the concept of "fumbles as personal experiences that only impact the character directly" and no concept of making the scene more complex, with players that are the focus of unfriendly attention requiring the party to take steps to keep them alive as much as defeat their enemy and thus making the scene more complex and requiring special actions that wouldn't otherwise be undertaken, like bullrushing undead away from fallen allies to prevent the undead from making coup de grace attacks.
The fact that my game only has the concept of what you call a fumble, and no mechanical implementation of what you call a failure, and yet frequently has fumbles escalate the challenge on the party as a whole suggests to me that your definition is flawed.
